1. Field of the Invention
The present invention relates to electrical power generators, and more particularly to an optimum channel or nozzle configuration for a device generating useful electrical power by means of an electrohydrodynamic (EHD) process.
2. Description of Prior Art
An EHD device uses the flow of fluid, usually a gas such as air or water vapor, in which are entrained a very large number of very fine and well distributed solid or liquid particles, such as water droplets as in an aerosol spray, the particles being electrically charged and of one polarity. The fluid flows through a nozzle-like channel by the imposition of a suitable pressure drop. The charged particles are introduced into the fluid flow by a suitable injector upstream of the nozzle-like channel input and are removed from the flow by a suitable collector at some downstream location. (See U.S. Pat. No. 3,777,564 entitled "Electrogasdynamic Spectral Anemometer" issued to Oscar Biblarz on Dec. 11, 1973 and co-pending U.S. patent application Ser. No. 93,790 entitled "Changing Mechanisms for Electrogasdynamic Spectral Anemometer" filed by Oscar Biblarz on Nov. 13, 1979 for examples of charging and collecting mechanisms.) The charged particles constitute an electrical current moving through an electrical field which exerts forces upon the particles in a direction and sense opposed to the general fluid motion. Work results from moving the particles against the resistance of the electrical forces which causes a corresponding decrease in the total enthalpy of the fluid stream. The work creates a difference in electrical potential between the input and the output which are connected to an external useful electrical load. Thus, the enthalpy drop of the fluid is converted into a useful electrical power output without the use of any major rotating or reciprocating components.
The performance of an EHD device is limited by the maximum electrical field strength that can be sustained at the most critical point in the field without inducing electrical breakdown, typically at the point of injection. But the presence of a maximum field at the beginning of the EHD conversion channel limits performance severely because the rest of the channel operates below maximum capacity, i.e., the electric pressure is at its allowable limit in only a small fraction of the conversion channel.
Therefore, it is desired to achieve greater power output per unit volume of channel by having a channel in which the local field strength is everywhere uniform close to the critical limit.